Japanese Patent Laying-Open No. 2009-105575 discloses a filter that prevents propagation of a high-frequency noise current to a cable through a connector. In the filter disclosed in Japanese Patent Laying-Open No. 2009-105575, a region exhibiting high impedance is formed in a peripheral portion of a connector of a printed circuit board. The region exhibiting high impedance has an electromagnetic band gap structure having a band gap that blocks propagation of electromagnetic waves in a prescribed frequency band. U.S. Pat. No. 6,483,481 discloses a surface structure exhibiting high impedance in multiple frequency bands.
The region exhibiting high impedance includes a plurality of small conductor pieces disposed at regular intervals on a first conductor layer, a ground conductor film disposed on a second conductor layer, and a conductor post connecting the plurality of small conductor pieces to the ground conductor film.